My 1991 Jeep Wrangler, 4 cylinder backfires when I get up around 40 or 50 MPH. It starts to loose power first then backfires. I re-gaped the plugs to specs., changed the fuel filter, but it still does it. I heard it may be the cat. converter. Please help me ...... Thanks

May be a vacuum problem at that speed.

check the injectors and make sure there is fire on those plugs in 3 and 4

Hello reconrandall,

For the 2.4 four cylinder the recommended plug is a Champion RE16MC gaped to .037 to .042 inches and for the 4.0 six cylinder, NGK ZFR5N gap to .030 to .035 inches.

I hope this helps.

Regards,

Jerry

1991 4 cylinder with no AC

Under hood, driver side, lower engine area, front of distributor, mounted in engine block.

It looks looks this;

Start with the basics...meaning check the spark plug wires and spark plugs. While under the hood, inspect all hoses for a vacuum leak(s). Then turn the ignition key on-off-on-off- on...leave in the on position and write down the number of flashes the check engine light indicates....2 flashes = #2....pause.....3 flashes = #3.
Let start from here. Are you able to perform engine repairs or diagnostics???

my guess is your timing could be off, or ^, plugs can be gaped wrong

Try to exchange the coil i

disconnect exhaust ,muffler or cat may be stopped up

Normally this sort of scenario indicates a sticking or broken EGR valve and/or a serious vacuum leak. Either of these will cause the problem you described.

Hope this helps you....